Every week I speak to women all over the world who (surprise!) have irregular periods, period pain, heavy periods, or periods that seem to be on permanent vacation.

Although we often talk about causes for these issues as they relate to hormones like estrogen and progesterone, what many women don’t realize is that the thyroid (and the several types of hormones it secretes) may also be to blame.

Thyroid dysfunction can cause longer and more frequent periods and interfere with ovulation, affecting your chances of not only have a normal period, but also your ability to get and stay pregnant (1).

Here’s the tricky thing about thyroid problems: What many doctors consider “normal” levels of thyroid hormones really aren’t, a fact that leaves many women undiagnosed and needlessly dealing with a range of period and fertility problems

Before we delve too deep into the link to these issues, however, first let’s talk about what the thyroid’s function is and how it works in your body.

What is the thyroid?

Your thyroid is a butterfly-shaped gland that sits on the front, lower part of your neck. If you have ever had a doctor examine your thyroid, you know exactly where it is—and how it’s a bit uncomfortable when you press on it.

Think of the thyroid gland as the master control center for your body, producing hormones that regulate your body’s metabolism, heart rate, and body temperature. These hormones—known as triiodothyronine (T3) and thyroxine (T4)—are converted from iodine by the thyroid gland, but only a small amount of T3 (the hormone recognized by your cells) is produced in this way. As a result, the body relies on the conversion of T4 into T3, which happens in the liver, gut, kidneys, and brain, into T3 to keep you feeling like your energetic and healthy self.

The thyroid hormones don’t work alone within your body, however. They may control a lot but they must work with your other hormones so you can have regular periods and get pregnant—if you want to, of course!

What causes thyroid problems?

There’s no one clear-cut cause of thyroid dysfunction so it could be one or a combination of these:

  • Stress
  • Environmental toxins
  • Genetics
  • Nutritional deficiencies such as iodine deficiency
  • Lifestyle factors
  • Pregnancy
  • Smoking or other chemical stressors
  • Other autoimmune conditions or diseases

The Thyroid and Your Menstrual Cycle

When your thyroid is functioning properly, T3 and T4 are produced/converted in amounts ideal for supporting a healthy cycle and optimal fertility. Conversely, thyroid hormones that are chronically too low (known as hypothyroidism) or too high (aka hyperthyroidism) can cause light, heavy, irregular, or nonexistent periods and disrupt ovulation.

This ovulatory disruption results in progesterone deficiency by interfering with pituitary hormone production (in particular prolactin, FSH, LH), thus messing with the ovulatory process beginning in the brain. Additionally, hypothyroidism deprives your ovarian follicles of the thyroid hormone they need to develop (1).

I dive deeper into the thyroid-menstrual cycle connection in this post, but generally speaking, a low-functioning thyroid robs the entire body of energy, especially of that needed to keep the reproductive system up and running as it was designed. Understandably, the body just can’t put energy into ovulation when it is running on an energy deficit and feels like it’s struggling to stay afloat.

Keep in mind, ovulation is absolutely necessary for getting pregnant—without the release of an egg, conception cannot occur.

Not only is thyroid dysfunction linked to irregular periods and infertility, but it’s also associated with problems during pregnancy like miscarriage, preeclampsia, poor fetal growth, premature birth, and stillbirth (1).

On top of that, autoimmune thyroid conditions like Hashimoto’s Thyroiditis and Graves’ disease affect up to 18 percent of women and can also interfere with your periods and your ability to conceive.

The Thyroid and Autoimmunity

Hashimoto’s Thyroiditis, the most common cause of hypothyroidism in the United States, causes the body to produce antibodies with instructions to destroy cells that resemble the hormone producing cells in the thyroid, or their receptors. The immune system doesn’t recognize thyroid tissue as friendly tissue and attacks it as though it’s a foreign body, gradually weakening its ability to produce adequate thyroid hormone.

If you have Hashimoto’s, you’ll potentially experience the symptoms described in the previous section. Read more about how hypothyroidism can affect your menstrual cycle here.

Hyperthyroidism, or an overactive thyroid—as seen in the autoimmune condition Graves’ disease, another situation in which the thyroid is under attack—is less common than hypothyroidism, but has similar effects on fertility. Since there’s too much thyroid hormone being produced and circulating in the bloodstream, the metabolism speeds up too much, often resulting in infrequent periods or missing periods. According to a January 2015 study in the journal Obstetrician & Gynaecologist, 2.3 percent of women with infertility also have an overactive thyroid. Read more about how hyperthyroidism affects menstrual cycle here.

How To Test Your Thyroid

If you suspect you have thyroid dysfunction, it’s important to get a comprehensive panel that screens all of the thyroid hormones. Some doctors may only screen for TSH and/or T4, but because of the complexity of thyroid function it’s important that you do a full test that screens for:

  • Thyroid Stimulating Hormone (TSH)
  • Free Thyroxine (FT4)
  • Free Triiodothyronine (FT3)
  • Thyroglobulin Antibodies (TGAB)
  • Thyroid Peroxidase Antibodies (TPO/TPEX)

This test from Lets Get Checked will give you a complete picture of what’s going on in thyroid land, and provide you with results in 2 to 5 days. (Use code HORMONES20 to get 20% off the price of the test!)

Once you get tested, I highly recommend looking at the results according to the generally accepted functional or optimal ranges.

TSH: 0.5-2.0 mIU/L
Total T3: 100-180 ng/dL
Total T4: 6.0-12 µg/dL
Free T3: 2.5-4.0 pg/mL
Free T4: 1.0-1.5 ng/dL
Reverse T3: 9-21 ng/dL
TPO: 0-15 IU/mL
TGAB: 0-0.9 IU/mL

Not in range? Please work with a functional medicine or naturopathic doctor who can partner with you to find the underlying causes and provide sustainable solutions. Also, keep reading for my tips on natural thyroid support!

Natural Ways To Support Your Thyroid

Fortunately, there’s a lot you can do to support your thyroid.

Foods That Support The Thyroid

The following foods are rich in the nutrients listed above.

  • Cruciferous vegetables such as broccoli, cauliflower, kale, and Brussels sprouts
    (Worth noting: Some cruciferous veggies are high in goitrogens, a naturally-occurring substance that can disrupt the production of thyroid hormones by interfering with the thyroid’s ability to use iodine. Make sure to cook these foods well before consuming to reduce their goitrogenic impact, but also know this effect has likely been over-exaggerated and you shouldn’t skimp on these healthy foods.)
  • Wild-caught fish, especially salmon
  • Brazil nuts
  • Sea vegetables
  • Eggs
  • Strawberries

Specific Nutrients That Support The Thyroid


The thyroid is dependent on iodine to make thyroid hormones, and thyroid dysfunction worsens when iodine levels in the body are low. It’s important to get enough iodine from food sources like sea vegetables. Only add an iodine supplement if prescribed by your doctor—too much of this mineral can cause symptoms to worsen, especially for those with autoimmune thyroid conditions.


If have an iron deficiency, your thyroid is forced to conserve energy—a risk factor for lower thyroid hormone production. While it is possible to take iron supplements, it is better to obtain iron in its heme form, which is available only from animal sources like beef, lamb, and liver.  Take this Iron Test to get your iron levels checked.


Zinc is required to convert T4 to T3, the thyroid hormone that cells need to maintain optimal thyroid function. You can find zinc in beef, shrimp, kidney beans, spinach, and flaxseed. If you take a zinc supplement, the recommended dosage is 30 mg per day with meals to prevent nausea. Recommended brands include Thorne Research Zinc Picolinate and Pure Encapsulations Zinc Picolinate.


Along with zinc, selenium is required to convert T4 to T3 and it increases levels of glutathione, the body’s master antioxidant that majorly supports the immune system and lowers thyroid antibodies. If you have digestive problems like leaky gut syndrome or Crohn’s disease, you have a higher chance of being deficient.

Organic Brazil nuts are the best way to get selenium from food and you only need 1 or 2 per day to maintain selenium levels. If you prefer to supplement, the dosage is 200 mcg a day and these are recommended brands Pure Encapsulations Selenium (Selenomethionine) or  Life Extension Super Selenium. Don’t exceed 200 mcg a day.


Magnesium helps the thyroid gland make more T4 for conversion to T3. Abundant sources of magnesium include dark leafy greens, nuts, seeds, and whole grains. If you take a magnesium supplement, consider Seeking Health Magnesium Glycinate or Designs for Health Magnesium Chelate. Magnesium glycinate is one of the most easily absorbed forms of magnesium, which will prevent diarrhea. The recommended dose is 300 mg a day or follow label directions.

Vitamin D

Vitamin D helps protect the body from autoimmune diseases, especially Hashimoto’s. Vitamin D is in some fatty fish including mackerel, salmon, and tuna—as well as in cod liver oil.

Before taking a supplement, test your Vitamin D levels first because you do not want to supplement with this vitamin if you are not deficient. You can take this at home test from Lets Get Checked (use code LEAPYEAR29 to get 29% off).  If you are deficient, speak with your doctor to figure out the best dosage to get your levels back up, or consider taking 2000 IU a day which will maintain your current level. Seeking Health Vitamin D3 + K2 Liquid or Capsules.



  1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3136077/
  2. http://www.thelancet.com/journals/landia/article/PIIS2213-8587(17)30402-3/fulltext
  3. http://onlinelibrary.wiley.com/doi/10.1111/tog.12161/abstract